Theodor Svedberg

Swedish chemist

• Born: August 30, 1884
• Birthplace: Fleräng, Valbo, Sweden
• Died: February 25, 1971
• Place of death: Örebro, Sweden

Svedberg made extensive contributions to physical chemistry, especially to the subfield of colloid chemistry. He invented the ultracentrifuge, a device for determining the sizes, densities, and distribution of very small particles. He also invented a balance for measuring low osmotic pressures.

Primary field: Chemistry

Primary invention: Ultracentrifuge

Early Life

Theodor Svedberg (TAY-oh-dahr SVEHD-bahryuh) was born in Fleräng, a small town in Sweden northeast of Stockholm, to Elias Svedberg and Augusta Alstermark Svedberg. His father, a civil engineer who managed different ironworks in Sweden and Norway, strongly influenced his only child by fostering an interest in science and an enduring love of nature. Theodor sometimes performed experiments in a laboratory at his father’s workplace, and he regularly joined his father in long outings in the country.

Svedberg first attended the Köping School, then the Karolinska School in Örebro as well as the Gothenburg Modern School. Two teachers let him use the school laboratories after classes. He built a radio transmitter and a Tesla transformer and gave public demonstrations at the school. He also prepared chemicals at home. Svedberg’s love of nature drew him to botany, but he enjoyed physics and chemistry as well. He finally resolved to study chemistry, viewing it as a means to understand biological processes.

In 1904, Svedberg entered Uppsala University, where he received his bachelor’s degree in 1905, after only a year and a half of study. His first publication, on a new method for creating organic compounds of metals in colloidal form, appeared the same year. He presented his doctoral dissertation in 1907 and accepted an appointment as lecturer in Uppsala’s chemistry department.

Life’s Work

As a student, Svedberg became interested in the new field of colloid chemistry. Colloids are mixtures containing particles intermediate in size between ordinary molecules and larger particles visible with a microscope. These substances include the materials necessary for life (such as starch, cellulose, and proteins) and countless natural and manufactured materials (foods, paints, gels, soaps, alloys, rubber, fog). Though invisible to the eye, colloidal particles can be viewed indirectly by reflected light with an ultramicroscope, a device for studying particles too small to be seen with an ordinary microscope. Svedberg built an ultramicroscope and published several papers on the production and motion of colloidal particles before completing his dissertation on colloidal solutions. He believed his observations verified theories of Albert Einstein and Marian Smoluchowski about the chaotic movements of small particles, known as Brownian motion. Svedberg’s theoretical analyses were criticized by Einstein and Smoluchowski as well as by chemist Jean Perrin.

Radioactivity was also a new and exciting field at this time. Svedberg decided to determine where new radioactive substances might fit in the periodic table. Working with his colleague Daniel Strömholm, he found that corresponding members of the three radioactive series were extremely similar chemically. In 1909, Strömholm and Svedberg proposed that the periodic table based on atomic weight was only an approximation. Rather than being completely uniform in weight, elements were mixtures of chemically identical substances having slightly different weights. This was the earliest formulation of the concept of isotopes, a conceptual breakthrough with profound theoretical and practical consequences.

In 1912, Svedberg became the first professor of physical chemistry at Uppsala, a position that the university instituted for him. Colloids remained his main interest. Contrary to expectations, his research showed that colloids lacked properties that sharply distinguished them from other types of matter. Such findings eventually erased the distinction between colloid and physical chemistry.

Svedberg needed to use a centrifuge to progress in his work. This apparatus would apply extra force to the particles he was studying and cause them to sediment more rapidly. Since research funds were scarce after World War I, he became discouraged.

A visiting position at the University of Wisconsin at Madison in 1923 was a godsend. Svedberg thrived in Madison’s stimulating atmosphere. With J. B. Nichols, he built a centrifuge in which the sedimentation process could be recorded by photography. However, technical problems precluded useful measurements.

Rejuvenated by the Wisconsin experience, Svedberg returned to Sweden full of ideas and enthusiasm. In 1924, he and Hermann Rinde built the first working centrifuge for investigating colloids. They named this device the “ultracentrifuge,” following the pattern used for the terms “ultramicroscope” and “ultrafiltration.” Driven by an electric motor, this machine could rotate up to 8,700 times per minute and create a force up to 5,000 times the gravitational field.

Svedberg decided to use the ultracentrifuge to find the size distribution and molecular weights of proteins, which chemists believed were not uniform in size. To his surprise, tests with hemoglobin showed that all the particles were the same size. Just as amazing was the result that the molecular weight of hemoglobin was four times that predicted from its composition.

The first ultracentrifuge was unstable and unreliable, and it exhibited numerous problems. Explosions and breakage were common occurrences. Svedberg and his coworkers redesigned this device many times. Though it was suitable for many purposes, a different mechanism was needed to speed the centrifugation process and to enable researchers to distinguish components in a complex mixture.

In 1926, Svedberg and others constructed a high-speed ultracentrifuge powered by an oil-driven turbine instead of an electric motor. Early versions could rotate approximately 45,000 times per minute, producing a force approximately 100,000 times that of gravity. While working on this machine, Svedberg was awarded the 1926 Nobel Prize in Chemistry for his work on colloidal systems.

The award enhanced Svedberg’s status. The Swedish legislature agreed to fund a physical chemistry laboratory, which was completed in 1931. Privately, Svedberg felt that the award was premature. The Nobel Committee had thought that his early incorrect theoretical work corroborated the existence of molecules. He resolved to prove himself worthy of the award and threw himself into a whirlwind of activity. He concentrated on improving the ultracentrifuge and using it to study proteins and other large molecules.

During World War II Svedberg worked on synthetic rubber production. With a coworker, he invented a balance for finding molecular weights of polymers by osmosis in 1944. He also investigated the actions of radiations on proteins and built a neutron generator for such tests and to prepare radioactive tracers.

Svedberg was interested in relationships between academia and industry, and he was instrumental in founding the Research Council for Technology. He obtained funding from an industrialist to build a large cyclotron for research and medical applications. This machine was ready in the new Gustaf Werner Institute in 1949, the year of Svedberg’s mandatory retirement. Svedberg became head of the institute, where he continued research and collaborations with Swedish industries until his second retirement in 1967.

So closely was Svedberg associated with the ultracentrifuge and the researches this invention made possible that his peers named a measurement unit after him. The svedberg (S or Sv) equals 10^-13 seconds. It is used to measure the sedimentation rate of a suspended particle moving at constant speed.

Svedberg received numerous awards and honorary degrees, and he was elected to more than thirty learned societies, including the Royal Society in London and the American National Academy of Sciences. He died in Örebro on February 25, 1971.

Impact

Svedberg was a brilliant, innovative, and indefatigable researcher whose research and inventions advanced several scientific areas and contributed to the birth of a new field, molecular biology. His work had far-reaching consequences for areas as diverse as chemistry, biology, medicine, metallurgy, manufacturing, nuclear science, agriculture, and food processing.

Svedberg’s radiochemical investigations helped establish the existence of isotopes, which have had extensive applications in research, medicine, archaeology, technology, and industry. Radioactive isotopes are widely employed as tracers to mark nonradioactive elements, allowing researchers to follow physiological and industrial processes and chemical reactions.

Svedberg made his most significant contributions to the field of colloid chemistry. Directly and through his students, Svedberg established the existence of macromolecules, found the weight of many proteins and other substances, and determined that proteins were well defined in size. Svedberg’s research and invention of the ultracentrifuge sparked an explosion of research on the large molecules that compose living things, facilitating the identification of viruses and the development of modern biochemistry. He contributed to conceptual change in chemistry by showing that colloids lacked unique properties and establishing the existence of macromolecules, which became the new disciplinary focus.

Svedberg transformed physical chemistry in Sweden by building up the University of Uppsala’s chemical laboratories and mentoring numerous students. He created a fruitful exchange between academic and industrial research in Sweden by his individual efforts and through his work with the Research Council for Technology. Under Svedberg’s leadership, the Gustaf Werner Institute advanced research on radiation, its effects on macromolecules, and its applications to medicine.

Bibliography

Claesson, Stig, and Kai O. Pedersen. “The Svedberg.” Biographical Memoirs of Fellows of the Royal Society 18 (1972): 595-627. Two colleagues present details of Svedberg’s early life and his scientific career, including a comprehensive account of his research interests and accomplishments. Portrait, bibliography.

Ede, Andrew. The Rise and Decline of Colloid Science in North America, 1900-1935. Burlington, Vt.: Ashgate, 2007. Ede charts the rise and degeneration of colloid chemistry, showing how research questions and concepts changed even as the objects and equipment to study colloids endured. These changes made colloids irrelevant as an explanatory concept and led scientists to focus on macromolecules. Illustrations, tables, bibliography, index.

Holmes, Frederic L. Meselson, Stahl, and the Replication of DNA. New Haven, Conn.: Yale University Press, 2001. Exhaustive account of a classic experiment that concentrates on experimental practices and their complexity. Includes extensive description and analyses of the ultracentrifuge machine used by Matthew Meselson and Franklin Stahl and its associated theory and methods. Illustrations, index.

Kerker, Milton. “The Svedberg and Molecular Reality: An Autobiographical Postscript.” Isis 77 (1986): 278-282. Kerker analyzes Svedberg’s work on Brownian motion, arguing that Svedberg was misled by faulty assumptions. Svedberg’s Nobel Prize was awarded in part for this ingenious but erroneous work. In time, Svedberg and others ceased to cite it. Includes an excerpt from Svedberg’s autobiographical notes describing his reactions to the award. Illustrations, notes.

Svedberg, Theodor, and Kai O. Pedersen. The Ultracentrifuge. Oxford, England: Clarendon Press, 1940. Detailed and authoritative description of ultracentrifuges, including their construction, operation, measurement methods, and theory, plus results obtained for proteins and organic colloids. Illustrations, tables, bibliographies, indexes.